[Nagiosplug-help] check_dhcp across subnets

Holger Weiss holger at CIS.FU-Berlin.DE
Thu Mar 13 11:44:09 CET 2008

* Ian Rarity <Ian.Rarity at espc.com> [2008-03-13 09:17]:
> DHCP requests won't get passed outside the subnet that they're
> broadcasted in unless you specifically tell your routers to do so.

Or if you tell check_dhcp to pretend to be a DHCP relay using the "-u"
flag :-)  It'll then send a normal unicast packet which should be routed
as any other packet (unless it's filtered, of course).

> I wouldn't recommend that, though; you're probably better off using NRPE
> or something similar to do the check on the remote serer and pass the
> result back to your Nagios box.

That would be another option, but the "-u" flag should work just fine.

> Scott Machtmes <scottm at brocade.com> 12/03/2008 21:23 >>>
> > I am using the latest check_dhcp plugin (check_dhcp v1810 nagios-plugins
> > 1.4.11). It works fine on the local subnet. I can't get it to work
> > across subnets to remote dhcp servers.

Do you see the request and a reply in the DHCP server's logs?  If so,
could you verify that the server's reply reaches the Nagios host using
tcpdump(8) (something like "tcpdump -vv port bootps")?


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